||A half-abstract base class that resource loaders' respective
channel-listening classes should derive from. Provides a unified API to
register the load or preload in a document scoped service, links <link
rel="preload"> DOM nodes with the load progress and provides API to possibly
consume the data by later, dynamically discovered consumers.
This class is designed to be used only on the main thread.
||This key is used for coalescing and lookup of preloading or regular
speculative loads. It consists of:
- the resource type, which is the value of the 'as' attribute
- the URI of the resource
- set of attributes that is common to all resource types
- resource-type-specific attributes that we use to distinguish loads that has
to be treated separately, some of these attributes may remain at their
||Intended to scope preloads and speculative loads under one roof. This class
is intended to be a member of dom::Document. Provides registration of
speculative loads via a `key` which is defined to consist of the URL,
resource type, and resource-specific attributes that are further
distinguishing loads with otherwise same type and url.